set uniform weight on component
For this kind of mechanical weight-assignment..
Through the 'Vertex Groups' panel in the object's Data tab

Select the vertices whose weights you want to modify
With the relevant group selected in the panel, set the value in the slider beneath it, and hit 'Assign'.

Or, in Edit mode, Vertex.. ( it might help to have 'Vertex Group Weights' checked in the Overlays, to see the weights as colors)

If the  active vertex is in an existing vertex group, then the Vertex Weights  dropdown will appear, as shown



Set the weight of the active vertex, in the indicated group.
Hit 'Copy' to copy the weight to the other selected vertices

Or, in Weight Paint mode..


With Vertex Masking switched on, and having tabbed out to make your vertex selection and back again, if necessary
Hit ShiftK to fill the selection with the current Brush setting.